PHYLOGENY 



435 



with a comparatively scanty amount of strobili, and still less of 

 gametophytic structures. Consequently, theories have been based 

 almost entirely upon comparative anatomy of the sporophyte. 



According to Jeffrey, the most profound student of anatomy 

 America has produced, and who, with his students, has developed 

 the subject of comparative anatomy from both the phylogenetic and 

 ecological standpoints, making abundant use of Mesozoic and 

 Paleozoic material, the Abietaceae are the ancestral stock from 



Thc/ocorpineae^^ 



Corda/fa/es 



Fig. 396. — Genealogical tree of the Coniferales, showing their proximity to the Gink- 

 goales. — After Jeffrey.^"' 



which the other five famihes have been derived. His views in regard 

 to relationships in the coniferophyte phylum are summarized in a 

 diagram taken from his book. The Anatomy oj Woody Plants (fig. 396) . 



Some of the evidence for and against a derivation of the Abieta- 

 ceae from the Cordaitales is as follows: 



In spite of the antiquity of spur shoots in Ginkgoales and early 

 members of the Abietaceae, the spur shoot must be regarded as a 

 later development. The long shoot was the original form of the plant 

 body. There are no spur shoots in the Araucariaceae, or in seedlings 

 of the Abietaceae. As far as the theory of recapitulation is con- 

 cerned, the long shoot is more primitive than the spur. 



